The present invention relates to lightning detectors capable of detecting, locating and determining the intensity of lightning discharges.
Present methods for locating lightning discharges are based in large part on providing instruments capable of detecting electromagnetic fields or optical transients produced by the discharge. Crossed-loop direction finders and other versions of sferics detectors are in common use as are cameras and T.V. systems. Unfortunately, however, the complex nature of the emitting source, as well as the rather long wavelengths involved, limit the accuracy of these electromagnetic field techniques. Photography, on the other hand, can provide accurate angular information but it is limited in time resolution and also by the fact that it entails rather slow processing of the data. Further, photography suffers during daylight because of film exposure. Other techniques include rather sophisticated T.V. systems utilizing video recording and, although these have fair accuracy and time-resolution, they obviously become rather expensive and cumbersome particularly when widely used for many field experiments.
Although, as far as is known, position sensing photodiode detector systems have not been used for locating such transient and spatially unpredictable events as lightning discharges, it is recognized that these detectors are well known and that they have been used for locating light sources of a rather wide variety. For example, U.S. Pat. No. 3,800,146 issued Mar. 26, 1974 to Brunkhorst, Carr and Dueker describes these light sensitive detectors in some detail and further identifies other U.S. patents in which the detectors are disclosed. In general, the detector of the type presently under consideration is a light sensitive device usually having pairs of opposed output electrodes at which quadrature signals are produced and the signals that are produced vary inversely with the distance from the location of the image or light spot impinging on the detector. Thus, when the image is closer to one output electrode than to the others, a larger signal is produced at the one electrode with the result that the position of the image on the detector can be determined by determining the fractional distribution of the quadrature outputs. However, as has been indicated, the potential of such conventional detector units for locating lightning discharges has not been recognized and, simple and effective systems for realizing this potential have not been realized.